1. Field of the Invention
This invention relates to a pneumatic power tool, more particularly to a pneumatic power tool with a torque controlled for automatic shut-off.
2. Description of the Related Art
Referring to FIGS. 1 to 3, a conventional power screwdriver 1 is disclosed in U.S. Pat. No. 5,201,374, and includes a pneumatic motor 12 received in a housing 11, a power control 16, and a torque responsive override clutch 2 coupling the motor 12 to an output shaft 17. A power control actuating mechanism includes a push rod 14 which, in an entry state, rests against a transversely movable latch 21 and is released for axial displacement toward a shut-off state at relative rotation between driving and driven halves 24,23 of the clutch 2. The actuating mechanism further includes balls 273 disposed in peripheral pockets in one of the halves 24,23, either of which balls 273 is arranged to cooperate with the latch 21 to shift the latch 21 to an unlatched position to thereby make the power control 16 shut off the power supply to the motor 12 as the clutch 2 overrides at a desired torque level. However, the conventional power screwdriver 1 has a complicated construction with a large number of components and is therefore inconvenient to fabricate.